The present invention is directed to an improved cementitious composition and method of making the same. In particular, the invention is directed to additives which enhance the physical properties of cementitious compositions lending their application to anchor systems for use in the most adverse environments, i.e. undersea, desert, and alkaline soil conditions. A particular advantageous use is as the formation of undersea or sand anchors requiring little or no preparation or excavation of the soil substrate.
Generally, cementitious compositions are based upon mixtures of Portland cement with additives which impart certain desirable properties and are made for exposure to various environments. For instance, fatty acid esters are used as an additive to impart water repellency to the finished cement. Additives of this type are disclosed in U.S. Pat. No. 3,008,843, granted to Jolly (partial esters of common fatty acids), U.S. Pat. No. 3,656,979, granted to Striebel, et al. (tertiary, saturated aliphatic monocarboxylic acids), and U.S. Pat. No. 3,547,665, granted to Johnson (animal fat, glycerides, and fatty acid additives dispersed in water). Other patents disclose using acid ester additives to improve the compressive strength of cement mixtures, i.e. U.S. Pat. No. 3,537,869, granted to Proell (lecithins) and U.S. Pat. No. 4,286,992, granted to Galer et al., (hydroxy polycarboxylic acids). Other organic substances and oils are required to be included with many of these fatty acid additives for optimum performance. The amount of additive is often in excess of several percent of the cement's total weight. Even these large quantities do not achieve the result of the present invention, with attendant savings in cost. Besides the inherent problems of dispersing large quantities of organic additives in a cement mix, additional steps are often required after setting the cement. For example, heating the cement's surface to impart the desired properties is disclosed in U.S. Pat. No. 4,207,115, granted to Boehme et al. Moreover, the use of these additives in a cold environment is severely limited. Whereas, the present invention not only can be poured at freezing temperatures but can also use near-freezing water as a mixing agent.
Carbohydrate materials are commonly added to delay the setting time and increase the compressive strength of the cement. U.S. Pat. No. 3,432,317, granted to Kelly et al., and U.S. Pat. No. 4,058,407, granted to Ray, disclose polysaccharides and carob tree fruit, respectively, for these desired properties. The use of these additives in large quantities however, risks complete or severe inhibition of hydration and hardening. Further, the potential unavailability and cost of these additives warrant use of the alternate admixtures of the present invention. The novel combination of a carbohydrate with a fatty acid ester and an alkali metal carbonate is disclosed only by the present invention.
Alkali metal carbonates are known to increase the compressive strength of a cement. U.S. Pat. No. 2,806,530 granted to Binkley and its continuation-in-part U.S. Pat. No. 2,868,295 disclose lithium carbonate as part of a treating agent applied to a cement filter cake under pressure. The Uchikawa et al., U.S. Pat. No. 3,819,389, discloses the use of alkali earth metals to make rapid hardening cement mixtures. U.S. Pat. No. 3,118,222 granted to Harris, and U.S. Pat. Nos. 3,139,351 and 3,223,542 granted to Hammer, disclose the use of alkali metal carbonates to improve the cosmetic appearance of the cement by reducing efflorescence and making a waterproofing solution for holes and cracks. Although lithium carbonate is known to increase the compressive strength of the cement, it has not been directly added as part of the cement mix, as per the present invention. Also, the present invention discloses a novel composition combining an alkali metal carbonate with a carbohydrate and a fatty acid ester.
Several problems have arisen in using cements containing additives found in the prior art under the adverse environmental conditions. For instance, undersea application has been complicated by the tendency of cements to disperse in water before completely setting. Sea currents and surges further complicate the integrity of the cement. These cements shrink, making structural degradation more probable. Contamination of the mixing water with either salt or dissolved mineral brines complicates mixing a proper cement formulation. The resultant cement products often exhibit degradation due to calcium sulfate rot and a loss in compressive strength. Also, the near freezing temperature of the mixing water and the similarly cold pouring conditions often prevent such cements from properly setting. Use of the cements for undersea anchor systems have exhibited cold-flow characteristics when placed under shear loads, leading to early failure of the anchoring system.
Similar problems arise when cements are used in anchoring systems under high alkaline soil conditions, i.e. deserts. The degradation and other problems which accompany use of prior art cements in this type of environment are eliminated by the cementitious compositions contained in the present invention.